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Cryomodule Helium Volumes. Tom Peterson, Fermilab AWLC14 13 May 2014. Introduction. Most helium inventory in a long string of TESLA/ILC-style cryomodules is in the helium vessels Most volume is in the 300 mm pipe
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Cryomodule Helium Volumes Tom Peterson, Fermilab AWLC14 13 May 2014
Introduction • Most helium inventory in a long string of TESLA/ILC-style cryomodules is in the helium vessels • Most volume is in the 300 mm pipe • During a power outage or severe cryogenic plant outage, the cryomodule string itself may act to provide temporary helium storage • The following provides a rough estimate of this storage capacity AWLC14, Cryomodules, Peterson
Cryomodule cross section AWLC14, Cryomodules, Peterson
Cryomodule helium inventory AWLC14, Cryomodules, Peterson
Closed-volume warm-up process • Assume valve control is available • Isolation of supply valves to 2 K space • Isolation valve closes on 2 K vapor return • Retain insulation vacuum and beam vacuum • Static heat load warms helium • Process is warm-up of the 2-phase system starting at 2.0 K, 31 mbar AWLC14, Cryomodules, Peterson
Results of first, coarse analysis XFEL AWLC14, Cryomodules, Peterson
What that table says • Warm-up from 31 mbar to 1.5 bar takes 39 hours • Assuming relief valves open at 1.5 bar, venting would begin at approximately 39 hours • Result is evaporation of almost all the liquid • Final state is almost pure vapor at 1.5 bar AWLC14, Cryomodules, Peterson
Sources of error, refinements • Seems nice, but • Thermal shield also warming up • Need second-order analysis incorporating slowly increasing static heat load • Still expect about one day before reaching venting pressure AWLC14, Cryomodules, Peterson
Conclusions • This is just an order-of-magnitude analysis • Nevertheless, it illustrates the potential of the cryomodule itself as a temporary storage volume during lack of cooling • Implementation requires supply and return valves closing to provide closed volume • Suggest further analysis and consideration of options • Secondary effect of slow thermal shield warm-up • Actual volumes including distribution system • Real practical venting pressures • Required valves and control for inventory management • Etc. . . . This is just a quick look. AWLC14, Cryomodules, Peterson